Group vi precursor compounds

ABSTRACT

The invention provides a facile process for preparing various Group VI precursor compounds, set forth below as Formula (I), useful in the vapor deposition of certain Group VI metals onto solid substrates, especially microelectronic semiconductor device substrates. Also provided is a process for the preparation of such precursor compounds. Additionally, the invention provides a method for vapor deposition of Group VI metals onto microelectronic device substrates utilizing the precursor compounds of the invention.

FIELD OF THE INVENTION

The present invention relates to certain precursors for the vapordeposition of Group VI-containing materials and to a method for theirpreparation.

BACKGROUND OF THE INVENTION

In consequence of its characteristics of extremely high melting point,low coefficient of thermal expansion, low resistivity, and high thermalconductivity, Group VI metals such as molybdenum, chromium, and tungstenare increasingly utilized in the manufacture of semiconductor devices,including use in diffusion barriers, electrodes, photomasks, powerelectronics substrates, low-resistivity gates, flat-panel displays, andinterconnects.

Such utility has motivated efforts to achieve deposition of molybdenum,chromium, and tungsten films for such applications that is characterizedby high conformality of the deposited film and high deposition rate toaccommodate efficient high-volume manufacturing operations. This in turnhas enabled efforts to develop improved molybdenum and tungsten sourcereagents useful in vapor deposition operations, as well as improvedprocess parameters utilizing such reagents.

However, certain of these precursors are solids at room temperature, andare otherwise challenging to use in vapor deposition processes.

SUMMARY OF THE INVENTION

The invention provides a facile process for preparing various Group VIprecursor compounds, set forth below as Formula (I), useful in the vapordeposition of certain Group VI metals onto solid substrates, especiallymicroelectronic semiconductor device and flat panel display substrates.The process provides an effective means to obtain and isolate suchmaterials, which can then be precursor sources of molybdenum, chromium,or tungsten-containing materials to be deposited on such substrates.Additionally, the invention provides a method for vapor deposition ofsuch Group VI metals onto microelectronic device substrates. Certain ofthe precursor compounds are solvates of the formula MO₂X₂L₁L₂, which areuseful both as Group VI precursor materials as well as being useful asintermediates in providing compounds of the formula MO₂X₂ in a vapordeposition system; in this regard, the formation of such solvates hasbeen surprisingly found to be readily reversible. This feature allowsone to prepare a solvate of the Formula (I) below, existing either insolid form or in a solution of the chosen solvent in liquid form, whichaids in the physical transport of such precursors within the vapordeposition delivery system, and then provides a precursor-solvate adductwhich can then be readily reconverted at a convenient juncture to theprecursor of Formula MO₂X₂ and utilized in vapor deposition processes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three-dimensional solid-state crystal structure depiction ofMoO₂Cl₂(CH₃OC(O)OCH₃)₂.

FIG. 2 is a three-dimensional solid-state crystal structure depiction ofMO₂Cl₂(CH₃CH₂OC(O)C(O)OCH₂CH₃)₂.

FIG. 3 is a graph of the thermogravimetric analysis comparing (i)MoO₂Cl₂, after reaction with dimethyl carbonate followed by drying, (ii)MoO₂Cl₂, and (iii) MoO₂Cl₂ after treatment with dimethyl carbonate toform the solvate in dimethyl carbonate solution.

FIG. 4 is a graph of the thermogravimetric analysis of theMoO₂Cl₂(diethyl oxalate) adduct.

FIG. 5 is a graph of the thermogravimetric analysis of theMoO₂Cl₂(propylene carbonate) adduct.

DETAILED DESCRIPTION OF THE INVENTION

In a first aspect, the invention provides a compound of the Formula (I)

wherein M is chosen from molybdenum, chromium, and tungsten, X is chosenfrom fluoro, chloro, bromo, and iodo, and each L₁ and L₂ are the same ordifferent and are chosen from C₁-C₆ alkyl carbonates and C₁-C₆ alkyloxalates.

In one embodiment, the C₁-C₆ alkyl carbonates include dimethylcarbonate, propylene carbonate, and the like. In another embodiment, theC₁-C₆ alkyl oxalates include dimethyl oxalate, diethyl oxalate, and thelike.

In a second aspect, the invention provides a process for preparingprecursors of the Formula (I), which comprises contacting a compound ofthe formula

wherein M is chosen from molybdenum, chromium, and tungsten, and X ischosen from fluoro, chloro, bromo, and iodo, with a compound of theformula L₁ and/or L₂, wherein L₁ and L₂ are the same or different andare chosen from C₁-C₆ alkyl carbonates and C₁-C₆ alkyl oxalates.

In one embodiment, the process is conducted at elevated temperatures,for example from about 20° C. to about 100° C.

It will be appreciated that the structure above depicting the compoundsof the invention is drawn in a two-dimensional format, not necessarilyrepresenting its three-dimensional orientation.

The invention affords certain compounds which are useful in the vapordeposition of Group VI metals onto various substrates, includingmicroelectronic semiconductor device substrates. Thus, in a thirdaspect, the invention provides a process for forming a molybdenum,chromium, or tungsten-containing material on a substrate, comprisingcontacting the substrate with a compound of Formula (I)

wherein M is chosen from molybdenum, chromium, and tungsten, X is chosenfrom fluoro, chloro, bromo, and iodo, and each L₁ and L₂ are the same ordifferent are and chosen from C₁-C₆ alkyl carbonates and C₁-C₆ alkyloxalates, and depositing the molybdenum, chromium, ortungsten-containing material onto the substrate, under vapor depositionconditions.

As noted above, the compounds of Formula (I) are useful in their ownright as (solid) precursors in the vapor deposition of certain Group VImetals, but they are also useful as intermediates in preparing compoundsof the formula MO₂X₂, and as such, and given their liquid form while insolution (i.e., with C₁-C₆ alkyl carbonates and/or C₁-C₆ alkyloxalates), are more easily transported within the vapor depositiondelivery and re-fill system, and then can be either used as is (solvatedform) or readily converted to the underlying compound of the formulaMO₂X₂ at a desired juncture, by removal of L₁ and L₂. Accordingly, in afurther aspect, the invention provides a process for forming a Group VImetal-containing material on a substrate in a reaction zone, saidreaction zone existing within a vapor deposition system having differentregions, comprising

-   -   (i) reacting in a first region, a compound of the formula MO₂X₂,        wherein M is chosen from molybdenum, chromium, and tungsten, and        wherein X is chosen from fluoro, chloro, bromo, and iodo, with a        with a compound of the formula L₁ and/or L₂, wherein L₁ and L₂        are the same or different and are chosen from C₁-C₆ alkyl        carbonates and C₁-C₆ alkyl oxalates, to provide a compound of        Formula (I):

-   -   (ii) transporting the compound of Formula (I) to a second region        in the vapor deposition delivery and re-fill system;    -   (iii) followed by removal of L₁ and L₂ by application of        sufficient heat and/or vacuum to volatilize any solvent present        to form a compound of the formula MO₂X₂, followed by    -   (iv) contacting the substrate with a compound of the formula        MO₂X₂ in a reaction zone, and depositing Group VI        metal-containing material onto the substrate, under vapor        deposition conditions.

As noted above, we have found that precursors of the Formula MO₂X₂readily form reversible solvates with C₁-C₆ alkyl carbonates and C₁-C₆alkyl oxalates. The solvates of Formula (I) thus formed can be used invapor deposition processes as Group VI precursors in an isolated solidform or can be dissolved in the C₁-C₆ alkyl carbonates and/or C₁-C₆alkyl oxalate solvents and used as liquid precursors, whereby suchliquid precursors would be delivered to a region adjacent to the vapordeposition reaction zone where any such solvent can be removed, eitherimmediately prior to injection into the vapor deposition reaction zoneor as the liquid is being injected into the vapor deposition reactionzone. In one embodiment, the liquid is flash vaporized as the compoundshown in Formula (I). In another embodiment, the solvent is removed fromthe liquid source of Formula (I), leaving MO₂X₂, as a pure solid. Inthis regard, given the challenges accompanying handling and otherwiseutilizing a solid form of precursors of the formula MO₂X₂, the solutionof the compound of Formula (I) in C₁-C₆ alkyl carbonates and/or C₁-C₆alkyl oxalates can be administered to a zone of the vapor depositionsystem prior to injecting same to a reaction zone where the vapordeposition takes place, either with or without removal of the C₁-C₆alkyl carbonate or C₁-C₆ alkyl oxalate solvent(s).

In a further embodiment, a solid precursor of the formula MO₂X₂ can beutilized in conjunction with a vapor deposition system with a source ofC₁-C₆ alkyl carbonates and/or C₁-C₆ alkyl oxalates nearby adjacentthereto, which can then be utilized to solubilize the solid precursor ofthe formula MO₂X₂, thus forming a liquid form of the compound of Formula(I) in the C₁-C₆ alkyl carbonates and/or C₁-C₆ alkyl oxalates solvent.In this regard, we believe that solutions of at least about 1 Molarconcentrations of Formula (I) can be formed in such C₁-C₆ alkylcarbonate and/or C₁-C₆ alkyl oxalate solvents, thus being efficaciousfor use as a liquid precursor source for Group VI metals.

In certain embodiments of the invention, the precursor can used inconjunction with pulsed vapor deposition conditions. It is expected thatthis will improve step coverage of the deposition. Suitably, the “pulse”and “purge” time of pulsed deposition may each independently be in therange of from 1 to 120 seconds, 1 to 60 seconds, or 1 to 20 seconds,depending on the substrate structure and reactor design.

In various embodiments, the vapor deposition conditions comprise aninert atmosphere, save for the optional presence of a reducing agentsuch as hydrogen. In certain embodiments, the precursor vapor may bedeposited in the substantial absence of other metal vapors.

The process of the present invention may comprise volatilizing thecompounds of Formula (I) or MO₂X₂ vapor, (for example, molybdenumdioxydichloride (MoO₂Cl₂) to form the molybdenum dioxydichloride(MoO₂Cl₂) vapor) for the vapor deposition operation. The vapordeposition conditions may be of any suitable type, and may for examplecomprise a reducing ambient (vapor) such as hydrogen gas so that theGroup VI-containing material comprises elemental Group VI metal materialin the deposited film. The Group VI metal-containing material sodeposited may comprise, or alternatively consist, or consist essentiallyof, elemental Group VI metals such as molybdenum, or molybdenum oxide,or other molybdenum-containing material. Depending on the level ofreducing agent, e.g., hydrogen concentration, it is possible topreferentially deposit greater proportions of elemental Group VI metalversus the Group VI metal oxide.

In one embodiment, the Group VI-containing layer deposited on thesubstrate surface may for example be formed by pulsed chemical vapordeposition (CVD) or atomic layer deposition (ALD) or other (thermal)vapor deposition technique, without the prior formation of a nucleationlayer and thus directly with MO₂X₂ or MO₂X₂L₁L₂ vapor. The respectiveprecursor vapor contacting steps may be carried out alternatingly andrepetitively for as many cycles as are desired to form the desiredthickness of the Group VI metal-containing film. In various embodiments,the contact of the substrate (e.g., titanium nitride) layer with thecompounds of Formula (I) or MO₂X₂ vapor is conducted at temperature in arange of from 300° C. to 750° C. for vapor deposition.

With such precursor vapor, the Group VI metal-containing material can bedeposited directly onto the substrate, to form a bulk deposit ofelemental Group VI metal or metal oxide or other Group VI-containingcompound or composition (i.e., MN) The concentration of H₂ is criticaltowards the formation of Group VI metal vs. oxide, as greater than fourmolar equivalents or an excess of H₂ is required for metal formation.Less than four (4) molar equivalents of H₂ will result in the formationof varying amounts of an oxide of the Group VI metal, and thus willrequire further exposure to H₂ in order to reduce the Group VI metaloxide thus formed.

The process chemistry for depositing such Group VI metal-containingmaterials in accordance with the present disclosure may includedeposition of elemental molybdenum, Mo(0), by the reaction2MoO₂Cl₂+6H₂→2Mo+4HCl+4H₂O. Intermediary reactions may be present andare well known in the art.

The Group VI metal-containing material deposited in accordance with themethod of the present invention may be characterized by any appropriateevaluation metrics and parameters, such as deposition rate of the GroupVI metal-containing material, film resistivity of the deposited Group VImetal-containing material, film morphology of the deposited Group VImetal-containing material, film stress of the deposited Group VImetal-containing material, step coverage of the material, filmcomposition and purity, and the process window or process envelope ofappropriate process conditions. Any appropriate evaluation metrics andparameters may be employed, to characterize the deposited material andcorrelate same to specific process conditions, to enable mass productionof corresponding semiconductor products and flat panel displays.Advantageously, the process of the invention is believed to be capableof depositing a film of high purity Group VI metal onto a semiconductordevice.

In certain embodiments, the invention relates to a method of forming aGroup VI metal-containing material on a substrate, comprising depositingsuch metals on the substrate surface by a chemical vapor deposition(CVD) process utilizing precursors described above, to produce the GroupVI metal-containing material on the substrate. In one embodiment, theGroup VI metal is molybdenum.

The substrate utilized in the deposition process of the invention may beof any suitable type, and may for example comprise a semiconductordevice substrate, e.g., a silicon substrate, a silicon dioxidesubstrate, or other silicon-based substrate. In various embodiments, thesubstrate may comprise one or more metallic or dielectric substrates,for example, Co, Cu, Al, W, WN, WC, TiN, Mo, MoC, SiO₂, W, SiN, WCN,Al₂O₃, AlN, ZrO₂, HfO₂, SiO₂, lanthanum oxide (La₂O₃), tantalum nitride(TaN), ruthenium oxide (RuO₂), iridium oxide (IrO₂), niobium oxide(Nb₂O₃), and yttrium oxide (Y₂O₃).

In certain embodiments, for example in the case of an oxide substratesuch as silicon dioxide, or alternatively a silicon or polysiliconsubstrate, the substrate may be processed or fabricated to include abarrier layer thereon, e.g., titanium nitride, for subsequentlydeposited material.

In one embodiment, the molybdenum, chromium, or tungsten-containinglayer deposited on the substrate surface may for example be formed bypulsed chemical vapor deposition (CVD) or atomic layer deposition (ALD)or other vapor deposition technique, without the prior formation of anucleation layer and thus directly with vapor derived from the compoundsof Formula (I) or from compounds of the Formula MO₂X₂, which areobtained from the compounds of Formula (I).

With vapor derived from compounds of Formula (I), the Group VImetal-containing material can be deposited directly onto the substrateto form a bulk deposit of elemental molybdenum, chromium, or tungsten ortheir corresponding oxides. With the addition of NH₃ as a co-reactant,the formation of MN can also be realized.

In another embodiment, an oxidizing co-reactant such as oxygen may beadded to the process when using the precursors as described herein as ameans of depositing a metal oxide thin film, such as MoO₂, WO₃, orCr₂O₃.

It will be appreciated that the method of the present invention may becarried out in numerous alternative ways, and under a wide variety ofprocess conditions. The process of the invention may for example becarried out in a process for making a semiconductor device on thesubstrate. The semiconductor device may be of any suitable type, and mayfor example comprise a DRAM device, 3-D NAND device, or other device ordevice integrated structure. In various embodiments, the substrate maycomprise a via in which the Group VI metal-containing material isdeposited. The device may, for example, have an aspect ratio of depth tolateral dimension that is in a range of from 10:1 to 40:1. In otherembodiments, the method may be carried out in the manufacture of asemiconductor device product, such as a mobile device, a logic device, aflat-panel display, or an IC packaging component.

The invention has been described in detail with particular reference tocertain embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

1-8. (canceled)
 9. A process for forming a molybdenum, chromium, ortungsten-containing material on a substrate, comprising contacting thesubstrate with a compound of Formula (I)

wherein M is chosen from molybdenum, chromium, and tungsten, X is chosenfrom fluoro, chloro, bromo, and iodo, and each L₁ and L₂ are the same ordifferent are and chosen from C₁-C₆ alkyl carbonates and C₁-C₆ alkyloxalates, and depositing the molybdenum, chromium, ortungsten-containing material onto the substrate, under vapor depositionconditions.
 10. A process for forming a Group VI metal-containingmaterial on a substrate in a reaction zone, said reaction zone existingwithin a vapor deposition system having different regions, comprising(i) reacting in a first region, a compound of the formula MO₂X₂, whereinM is chosen from molybdenum, chromium, and tungsten, and wherein X ischosen from fluoro, chloro, bromo, and iodo, with a with a compound ofthe formula L₁ and/or L₂, wherein L₁ and L₂ are the same or differentand are chosen from C₁-C₆ alkyl carbonates and C₁-C₆ alkyl oxalates, toprovide a compound of Formula (I):

(ii) transporting the compound of Formula (I) to a second region in thevapor deposition delivery and re-fill system; (iii) followed by removalof L₁ and L₂ by application of sufficient heat and/or vacuum tovolatilize any solvent present to form a compound of the Formula MO₂X₂;followed by (iv) contacting the substrate with a compound of the formulaMO₂X₂ in a reaction zone, and depositing Group VI metal-containingmaterial onto the substrate, under vapor deposition conditions.
 11. Theprocess of claim 10, wherein the compound of Formula (I) is isolated insolid form prior to being transported to either the second region or thereaction zone.
 12. The process of claim 10, wherein the compound ofFormula (I) is dissolved in a solvent chosen from C₁-C₆ alkyl carbonatesand C₁-C₆ alkyl oxalates.
 13. The process of claim 10, wherein thecompound of Formula (I) is injected by liquid delivery into a heatedzone for flash vaporization of the compound of Formula (I) and used todeposit a film onto a heated substrate in the reaction zone.
 14. Theprocess of claim 10, wherein the compound of Formula (I) is injected byliquid delivery metering directly onto a heated substrate in thereaction zone.